[X86] Use v4i32 vzloads instead of v2i64 for vpmovzx/vpmovsx patterns where...

[X86] Use v4i32 vzloads instead of v2i64 for vpmovzx/vpmovsx patterns where only 32-bits are loaded.

v2i64 vzload defines a 64-bit memory access. It doesn't look like
we have any coverage for this either way.

Also remove some vzload usages where the instruction loads only
16-bits.

llvm-svn: 364851